Means for improving the power factor of induction-machines.



A. SCHERBIUS.

MEANS FOR IMPROVING THE POWER FACTOR 0F !NDUCTION MACHINES.

APPLICATION FILED 01-:c. 12. 1911. 1,1 87,180.. 11116111611 June 13,1916.

' 4 SHEETS-SHEET 1.'

A. S'CHERBIUS.

MEANS FOR IMPROVING THE POWER FACTOR 0F mnucnou MACHINES.

APPLICATION FILED DEG-12,1911.

Patented June 13, 1916.

4 SHEETS-SHEET 2.

A. scnenmus. MEANS FOR IMPROVING THE POWER FACTOR 0F INDUCTION MACHINES.

APPLICATION FILED DEC- 12, I91]- I 1 1 87, 1 80'. Patented June 13,1916.

4 SHEETS-SHEET 3.

A. SCHERBIUS.

MEANS FOR IMPROVING THE POWER FACTOR 0F INDUCTION MACHINES.

APPLICATION FILED 051:.12, 1911.

Patented June-13, 1916. 1

4 SHEETS-SHEET 4.

UNITED s rarns PATENT OFFICE.

ARTHUR SGHERBIUS, 0F BADEN, SWITZEBLANDQASSIGNOR T0 AKTIENG IESELLSCHAFTBROWN BOVEBI & CIE., OF'B ADEN, SWITZERLAND. l

Specification of Letters Patent.

Patented June 13. 1916.

Application filed Decemlier 12, 191-1. Serial No. 665,207.

To all whom it may concern:

Be it known that I, AR'rnUn SoHEnnms,

a subject of the German Emperor, of Baden,

Switzerland, have invented certain new and useful Means for Improvingthe Power Factor of Induction-Machines, of which the following is aspecification. This invention relates to dynamo electric induction andlike machinery with especial reference to the phase compensation ofinduction motors. 7

It has already been proposed to compen sate the phase displacement of aninduction motor by connecting up a correspondingly excited commutatordynamo to its sliprings. Now with very large motorsit is frequently ofimportance automatically to obtain a good compensation under any load.However, with smaller units it will often suflic'e completely tosuppress the phase displacement only at the particular load mostgenerally present, for example at full'load, and to permit a certainphase displacement for the other working conditions. This will thenpermit the use of a machine of known arrangement without stator winding.

The main object of the present invention is to provide improved orsimplified means for phase compensation in induction motors;

The invention in brief consists in a construction and arrangement ofcommutator ferred to above'in which auxiliary poles are provided.

Referring to'the' accompanylng diagrammatic drawings which are given byway of example only :*Figure 1 shows the diagram of connections of anarrangement according to one form: of the present invention in which aninduction machine whose phase displacement is to be compensated 1s con-.

nected to a compensator machine without air gap between internal andexternal yokes. Flg. 2 shows diagrammatically a form of construction ofcompensator machine for compensating the phase displacement in atwo-phase machine. Fig. 3 is a vector diagram explaining the action ofthe compensator machine. Figs. 4 and 5 show in see tion and endelevation one construction of displaceable external iron system. Fig. 6represents a modification in which the air gap between the external andinternal yokes of the compensator machine is filled by a sol1d non-maetic. material. Figs. 7 and 8 show modi cations of the means forobtaining the desired saturation effect by suitable construction ofexternal yoke or teeth. Fig. 9 shows another modification in which largegrooves are provided partly filledif desired with iron or nonmagneticmaterial. Fig. 10 shows a further modification in which are providedremovable iron rings for the purpose of adjustingthe saturation effect.Fig. 11 is an explanatory diagram. Fig. 12 illustrates part of amodified arrangement in which resistances are added for effecting finalphase compensation. Fig. 13 is a vector diagram explaining the effect ofthe addition of resistance. 7 Fig. 14 shows an arrangement for effectingphase compensation automatically by the automatic insertion ofresistances. Fig. 15 is an explanatory diagram. Fig. 16 illustratesdiagrammatically a general arrangement of three-phase compensatormachine with ring winding, stationary brushes and auxiliary poles. Fig.17 shows a modified construction and arrangement in which auxiliarypoles are provided to act on the side of the internal yoke of thecompensator machine and the commutator thereof is formed on theperiphery of the moving member. Fig.

18 shows a similar construction of compensator to Fig. 17 but thecompensator is arranged for use with single phase machines,

.the auxiliary. poles having lateral projectionsfor providing a returncircuit for the auxiliary pole flux. Figs. 19 1::"d 20 llus- 'trate fa'further modified construction in which thefibrushes and auxiliary polesare adapted to rotate whereas the iron system with commutator remainsstationary.

In Fig. 1'5 is the induction motor whose I phase displacement is to becompensated.

The slip rings of this induction motor are connected by leads 8 tobrushes 12 of the compensator machine It. In the form illustrated inFi 1the compensator It comprises i an iron bo g r with windings r arrangedin grooves t erein' connected to the commutator z and mounted on'a shaft3 which may berotated by any suitable means such as an electric motor2.- The action of the compensator machine may best be understood byreference to Fig.2 in WhlCh 1s diagrammatically represented thecompensator with iron system 8 having windings thereon and a commutatora to which currents i and 11 are supplied from the machine to becompensated by means of brushes.

The 'following considerations apply n general for polyphasearrangements, but in the present case for the purpose of explanati onthe action of a two-phase arrangement will be considered. The current i,is always vectorially speaking displaced by 90 degrees in relation tothe current 1' The currents i, and 2', produce in the ring a fieldrotating at a speed c,,c,, a, being the slip periodicity of the twocurrents 1' i, and 0,, the

periodicity resulting from the speed and number of poles in thering.This rotating field produces in the windings coaxial to the axis of thebrushes through which the current i is passing a rotation voltage inphase with the current i, and this rotation voltage is consequentlydisplaced by 90 with respect to timeuin relation to the current i If thedirection of rotation of the ring be assumed to be the same as thedirection of phase-succession of the currents i rand i, then with to therotating field the ring rotates at a rate in excess of the synchronousspeed and acts as a capacity that isto say it produces currents leadingthe voltages. At first glance it would appear remarkable that a voltagecan be produced in a. machine without a fixed external yoke or whatpractically signifies'the same thing, without a stationary woundexternal system. It should be remembered, however that the current isabsolutely wattless'and' consequently with suchan arrangement noelectrical energ can be given out and a re-' ception of energy can takeplace only in I so far as this is possible in choking coils.

In the diagram Fig. 3, eis the slip-ring voltage of the machine whosephase displacement is to be compensated, i the slipring or brush currentis caused to lead e by the angle a and forms the magnetizing current forthe other phases 'of the commutator machine. The ohmic drop 21 'w isdisplaced by 180 degrees in relation to the current 11 and therotationvoltage e leads the current by 90 degrees. As the magnitudes a of allthese qualities v 'pbrtionally with the sl p, the angles of-theapproximately protriangle in 'the diagram remain constant undervariations of load and consequently also the phase displacement between0 and 1'. remains constant. The primary phase dlsplacement of themachine to be compensated,

owever, varies with,the load and consequently the phase compensationattained with the commutator machine connected up "in cascade, will beincomplete at other than normal load. I

As may be'seen from the-diagram, Fig. 3, the whole of the current ifsuplied to the compensator machine serves or magnetizadjustment of thecompensator machine.

Preferably some or all of the above means may be employed during theworking for entirely com ensating phase displacement at,

various 10a s-the corresponding manipulation being efl'ected by hand orautomatically.

In the form of construction shown by way of example in Figs. 4 and 5 thecommutato'r machine is constructed with an air gap between the internalyoke r and external yoke s by fastening the latter to the main shaft '2;by means of arms 0 and if necessary may be rendered adjustable byproviding a displaceable boss a as shown.

The air gap between external and internal yokes may be filled as in themodification shown in Fig. 6 with a solid nonmagnetic body 4 such aswood, both yokes being of course rotated together.

In Fig. 7 an air gap is arranged beneath a number ofthe teeth 11,whereas the remaining teeth 9 occasion the mechanical iron connectionbetween external yoke a and internal yoke r. A similar action to that ofan air ap can, as is Well-known, also be attained %yhigh iron saturationone arrangement for effecting this being shown in Fig. 8 in which theteeth are made wholly or partly very narrow. An adjustability of thesaturation of the machine can be attained by providin according to Fig.9 large grooves and fi ling them according to the desired effect partlywith iron. f or with non-magnetic material u.

If the region of high saturation be situate'in the outer yoke then forthe purpose of adjusting the saturation effect of the machine iron rings7' may be provided as shown in Fig. 1 0, which. may be detached axiallyfrom the exterior of the yoke a,

varying thereby the area of section of the magnetic paths in the saidyoke and consequently also the saturation effect.

Besides the advantages of constructive simplicity, economy of materialand cheapness,-the employment of high iron saturation in the compensatormachine has the further advantage that the compensation of the mainmotorcan' be extended to a much greater range of load than is possiblewhen unsaturated machines provided with an air gap are employed as isclear from Fig. 11 in which e shows the direction of the terminalvoltage of the compensated induction motor, 2' the stator current. Theend point of the .current vector 2', describes with varying load thecurve t shown in full lines in the case of unsaturated commutatormachines with air gap, whereas it describes the dotted curve i.- in thecase of highly saturated machines.

The phase displacement angle is shown by a and the magnetizing currentof the in-' duction motor by t It is evident from this figure that byproducing the effect represented by the dotted line the range ofapproximate phase compensation is extended since as the load rises thephase of 6 remains substantially constant according to the dotted curve,but continues to lag more and more according to the full line curve.

In certain circumstances it may be of advantage for the purpose of fineadjustment of phase to arrange resistances to reduce the current throughthe brushes. For example if the group be constructed with rotary brushesand fixed compensator as in the modification shown in Fig. 12, theresistance 'w may be electrically connected to the brush 7) and rotatedwith the brush spider b" which in turn may be mechanically coupled tothe rotor R of the induction motor, the latter being mounted in abearing Z on the standard 11 of which the fixed com pensator is mounted.The compensator is wound for example with a ring winding and is providedwith an internal commutator a with which the rotary brushes 6 contact.

The effect of the resistance may be easily appreciated on considerationof Fig. 13. If it be supposed that the compensator occasions asupercompensation correspondingly to the dotted lines of the diagram sothat the main current i in the stator of the induction rotor leads theline E. M. F. 6

by the angle a, the phase leading of the slipring voltage of thecompensator machine to the value e as indicated in Fig. 13. Without theparallel resistance w indicated in Figs. 12 and 14 the current in thecompensator would be equal to the rotor current i but with thisresistance the rotor cur rent 6 is split up into the compensator-currenti and the shunt current i possessing the same phase as 6 The remainingquantities in the diagram are self explanatory, to, being the rotorresistance of the induction motor and w the resistance of thecompensator.

If it be desired to obtain various phase compensations automaticallyduring worring, as may be the case for example with buffer plants, thenresistances are arranged external to the machine and are arranged to bedisplaced by a relay, which is actuated by changes of the power factorof the main ma 1 chine. One form of apparatus suitable for this purposeis indicated in Fig. 14 in which the main machine i and the compensatingmachine In are mounted on one shaft. The

effect of the resistances w is varied by means off the relay 5comprising a core 8 vwith a crosspiece carrying contact arms 9, which isoperated according to the power factor ex isting in the main machine bymeans of the coils 6 and 7 energized respectively in proportion to thecurrent and voltage of the main machine.

Considerations of sparklcss commutation enforce a restriction on theallowable output from compensators constructed according to the aboveexamples of carrying the present c #21) volts;

Hence with given commutator segment and brush dimensions the allowablecapacity of the machine is limited.

By the provision ofauxiliary poles however, to compensate the injuriousvoltages between the'brushes compensator machines may be constructed forany desired output. In order that auxiliary poles can really act on thearmature coils short circuited by the brushes, the armature coils mustcut the flux of the auxiliary poles at the current place. Now, however,normally the winding is surrounded on all sides by iron and is removedfrom the flux of external auxiliary poles and only when it is made as aring-w-inding are any portions of the winding situate on the outersurface of the machine. Consequently in applying the present invention aringwinning is provided in Fig. 16 in which is indicated a generalarrangement, h representing the auxiliary poles, 1" the ring-winding ands the commutator. The auxiliary poles are excited by the brush currentof one phase or of a combination of Several phases. In thearrangementshown in Fig. 17 ,"the

outwardly situated portion of the ring-windmg r 1S formed as acommutator 2, whereas the auxiliary poles it connected in series withauxiliary poles a connecting yoke for the.

same joining the auxiliary poles together is unnecessary, each of theauxiliary poles it being provided with one or two additional branches aby meansfof which the iron circuit of each auxiliary pole is closed. The

course of the magnetic flux of the auxiliary pole is indicated by dashesand that of the main field by chain lines. This arrangement hasthe'advantage of considerable economy of copper on the main coils as themagnetic circuit. by which the flux of the auxiliary poles is closed, inthis case only passes' through the armature ampere windings at theregion of commutation, whereas the other armature windings are situateoutside the path of the auxiliary pole flux.

It is evident that the invention can also be applied to dynamos withfixed winding and rotary brushes in which case the auxiliary poles andif necessary their yoke may rotate together with the brushes as shownfor example in Figs. 19 and 20 in which similar reference letterscorrespond to like parts 1n the preceding figures.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is 1. In dynamo electric machinery incombination, an induction motor with wound.

rotor, slip rings and brushes cooperating therewith, a dynamo electricphase compensating machine comprising an internal magnetic yoke, anexternal magnetic yoke, ex-

citing windings on one of said yokes, a commutator and brushescotiperating therewith,

a mechanical and magnetic connection be-. tween sald yokes, thedlmensions of the magnetic connection being such that saturation iseflected when the machine is in action means capable. of rotating theaforesaid magnetic yokes and a driving connection between said means andsaid yokes, together with electrical connections from the brushes of thephase compensating machine to the brushes of the induction motor.

2. A dynamo electric phase compensating machine comprisin meansproviding a magnetic circuit, inclu ing an internal magnetic yoke, anexternal magnetic yoke, a. mechanical connection between said yokes;winding disposed on one of said yokes adapted to saturate a portion ofthe magnetic circuit when the machine is in operation, a commutator andbrushes connected therewith, means for rotating said yokes andamechanical connection between said means and said yokes.

3. In dynamo electric machinery, in combination, an induction motor withwound rotor, slip rings and brushes cooperating therewith, a phasecompensating machine including a magnetic yoke, a further magnetic yokeexternal to the first yoke, teeth on one of the yokes, said teethforming both a me'-' chanical and a magnetic connection between saidyokes, windings-disposed on one of said yokes, a commutator and brushescooperating therewith, said windings being adapted to saturate theaforesaid teeth when the machine is in operation, means for rotatingsaid yokes and a mechanical connection between said means and one ofsaid yokes, together with electrical connections between the brushes ofthe compensating machine and the brushes of the induction motor.

4. A dynamo electric phase compensating machine comprising meansproviding a magnetic circuit, including a rotary magnetic yoke, anexternal magnetic yoke, a rigid mechanical connection between saidyokes, windings disposed on one of said yokes adapted to saturate aportion of the mag ARTHUR SCHERBIUS.

Witnesses:

HARRY A. MCBRIDE, AUGUST Riineo.

